[EKS] [request]: Enable HPAScaleToZero feature gate for EKS 1.16+/1.17+

### Community Note

* Please vote on this issue by adding a 👍 [reaction](https://blog.github.com/2016-03-10-add-reactions-to-pull-requests-issues-and-comments/) to the original issue to help the community and maintainers prioritize this request
* Please do not leave "+1" or "me too" comments, they generate extra noise for issue followers and do not help prioritize the request
* If you are interested in working on this issue or have submitted a pull request, please leave a comment

**Tell us about your request**
Kubernetes 1.16 added a feature flag `HPAScaleToZero` to allow HPA scaling to/from zero.
https://kubernetes.io/docs/reference/command-line-tools-reference/feature-gates/

**Which service(s) is this request for?**
EKS

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
We have pods for RabbitMQ consumers that are idling for a long time when the queue is empty. We want them to spawn only when the queue has some messages.

**Are you currently working around this issue?**
No.

The request concerns the Kubernetes HPAScaleToZero feature gate and AWS EKS, but names no repository files, tests, or implementation entry points. Start with the linked Kubernetes feature-gates reference and determine the EKS version and control-plane changes required; done would mean documented or delivered HPAScaleToZero support for the stated EKS versions.

Written by the indexing model from the issue text.